Television receiver tube



TELEVISION RECEIVER TUBE Fi1 ed July 14, 1934 INVENTOR J MAX Awou, BY

7 lawv ATTORNEY Patented Jan. 25, 1938 UNITED STATES PATENT OFFWE TELEVISION RECEIVER TUBE Germany Application July 14, 1934, Serial No. 735,098 In Germany July 31, 1933 1 Claim.

"Ithas already been proposed to use the Braun or cathode ray tubes, as television receiving devices. However, to this end it has in many instances been proposed to use only such Braun 5 tubes as those in which the concentration of the developed cathode rays is accomplished by means of a definite low gas pressure. In this case, the cathode rays behind the anode shutter are essentially parallel or they have only a very small angle 110 of divergence, so that the cathode ray beam has only a very small diameter at all places between the anode shutter and the luminous screen of the Braun tube. A cathode ray beam of small diameter produces at all points of the luminous 15 screen a sharp fluorescent spot, even if (and this is a fundamental fact for the present invention) the beam of rays passes through an inhomogeneous field between the deviation plates, which occurs in case of an insufiiciently large 20 width of the deviation plates. In making reference to width herein is meant the plate dimension at right angles to the tube axis. An inhomogeneous deviation field therefore can, in a Braun tube with ray concentration by means of gas fill- 5 ing, at the most lead to a change in the scale of the reproduction at the edges of the television picture, i. e. it may cause a distortion of the picture.

The invention is based upon the teaching that 30 in Braun tubes rarified to a high vacuum and in which the concentration of the rays is accomplished by means of electrostatically or magnetically acting condenser devices, for instance by means of concentration coils, the deviating course 35 of the cathode rays between anode shutter and luminous screen in tubes having gas filling, necessitates the observation of special rules in dimensioning the deviation plates.

In a tube equipped with a condenser device the 4 diameter of the ray between the deviation plates namely amounts to a multiple value of that in tubes with gas filling. This entails that the cathode ray beam, if it passes through an inhomogeneous field between the deviation plates, 5 is not deviated in an equal manner at all places of its cross section, but those rays passing through a stronger deviation field are more efiectively deviated than those passing through a weaker deviation field. Hence in the said case, the ray of 50 the cathode ray beam deviated in various manners will no longer be concentrated into a sharp point on the luminous screen. Therefore, in addition to the picture distortion noted in tubes having a gas filling, an indistinctiveness is obtained. 55 In order to avoid this disadvantage the width of the plates, i. e., the dimension at right angles to the tube axis is to be chosen, in a tube having a concentration arrangement, in a manner as indicated in the example of embodiment to be now described and which is shown by the accompany- 5 ing drawing, wherein:

Fig. 1 represents conventionally a cathode ray tube (envelope, electron source and other electrodes omitted for clearness of illustration) having deflecting plates formed according to this invention;

Fig. 2 is a section on line A-A of Fig. 1;

Fig. 3 shows a form of the invention wherein the two pairs of deflecting plates or electrodes are in the same plane at right angles to the tube axis;

and

Fig. 4 discloses a cathode ray tube embodying the system disclosed.

In connection with Fig. 1 the appearance of the blurring at the edges of the pictures which may occur in tubes having a concentration arrangement will be explained and likewise the dimensioning of the width of the plate to be carried out in accordance with the invention.

In Fig. 1, Ill signifies the luminous screen of the Braun tube, II is the concentration coil serving for the concentration of the rays, and I2 and 13 are the two pairs of deviation plates. The cathode ray beam is indicated by means of the two border rays thereof Hi and Hi. The cathode ray beam will be at first bent as is known, by the pair of deviation plates l2, thereby entering already eccentrically the pair of deviation plates 13 disposed at right angles to the pair of plates I2, as shown in Fig. 1 by means of the border rays I4 and I5 representing the deviated beam. The deviation plates l2 are also in part shown in' Fig. 2.

The cross section of the cathode ray beam in the section plane A-A is designated by Hi. If 4 the width b of the lower deviation plates i3 is taken too small, the individual rays of the beam in particular the rays hi and i5 are in differently strong deviation fields, since the field intensity at the place through which the border ray I5 passes, is appreciably lower due to the vicinity of the edge of the plate, than that at the place of the border ray It. Now the invention resides in selecting the width b of the plate suificiently large so as to eliminate the lack in distinctiveness pos- 5o sible due to this difference in the field intensity. For the plate arrangement shown in Figs. 1 and 2, the indistinctiveness at the edge of the picture will be negligibly small if the half width of the plate i. e. the value &1? is made larger than the value 5 in Fig. 1, i. e. the distance of the axis of the cathode ray beam from the tube axis the 'half diameter of the beam of the cathode rays Within the deviation plates l3.

In the arrangement of Fig. 3 deviation plates are so arranged that indistinctiveness at the picture edges is avoided in an adequate degree. By this arrangement if the Width b of all deviation plates is so chosen that the beam of the cathode rays, even if the luminous spot isin the corners of the picture, passes through a practically homogeneous field between the deviation plates. Hence the width b is to be taken so large that a homogeneous field exists for the one as well as the other of the pairs of deviation plates, above the cross section of the beam of cathode rays whose undeviated position is designated by Hi and also at the place I6" which may correspondv tube adapted to the described dimensioning of the deviation plates. Hereby the glass vessel has a narrower part l8 surrounded by the concentration coil l7, and a wider part. I9 containing the deviation plates. The upper deviation plates l2 may also be disposed within the narrower part I8. The parts l8 and [9 as shown in Fig. 4 are to have preferably a cylindrical shape.

Having thus describedthe invention, what I claim is:

In a cathode ray tube the combination comprising means to develop an electron beam, a first pair of deflecting plates, a second pair of deflecting plates positioned angularly with respect to the first pair of plates, said second pair of deflecting plates having a width greater than twice the sum of the maximum distance of the axis 'of the electron beam when defiected from the axis of the tube and half the diameter of the electron beam whereby the expanse of the field set up by the second pair'of plates is substantially greater than the field set up by the first pair of plates.

' MAX KNOLL. 

